1 82 ELEMENTS OF HISTOLOGY. [Chap. xxn. 



neck is the only portion of the intermediate part 

 present, e.g., in the sub-maxillary and orbital glands of 

 the dog and cat, and in the sub-lingual of the rabbit. 

 In others, especially in the serous salivary glands, as 

 the parotid of man and mammals, the sub-maxillary 

 of the rabbit and guinea-pig, and in the mixed salivary, 

 as the sub-maxillary and sub-lingual of man, there 

 exists after the neck a long intermediate part, which 

 gives off several shorter or longer branches of the 

 same kind, all ending in alveoli. 



243. The alveoli or acini are the essential 

 or secreting part of the gland ; they are flask-shaped, 

 club-shaped, shorter or longer cylindrical tubes, more 

 or less wavy, or if long, more or less convoluted ; 

 many of them are branched. Generally several open 

 into the same intermediate part of a salivary tube. 

 The acini are much larger in diameter than the 

 intermediate part, and slightly larger, or about as 

 large as the intralobular ducts. But there is a dif- 

 ference in this respect between the acini of a serous 

 and a mucous salivary gland ; in the former the acini 

 are smaller than in the latter. 



The membrana propria of the intermediate duct 

 is continued as the membrana propria of the acini. 

 This is a reticulated structure, being in reality a basket- 

 shaped network of hyaline branched nucleated cells 

 (Boll). The lumen of the acini is minute in the 

 serous, but is larger in the mucous glands ; it is 

 in both glands smaller during secretion than during 

 rest. 



244. The epithelial cells lining the acini are 

 called the salivary cells; they are of different 

 characters in the different salivary glands, and chiefly 

 determine the nature of the gland. The cells are 

 separated from one another by a fluid albuminous 

 cement substance. (1) In the serous or true salivary 

 glands, as parotid of man and mammals, sub-maxillary 



